1. Field of the Invention
The present invention relates to a battery. More particularly, the present invention relates to a battery having an electrode assembly including first and second electrode plates housed in a battery case, the battery configured to reduce or prevent the likelihood of an external impact causing a short circuit of the electrode assembly.
2. Description of the Related Art
Batteries are employed in a wide variety of equipment including, to name just a few, vehicles, e.g., electric and hybrid vehicles, portable power tools, electronics, etc. Portable compact electronic devices, e.g., cellular phones, laptop computers, camcorders, etc., are being widely developed and produced. Such portable electronic devices typically include an internal battery pack to allow continuing operation even in places where no external power supply is available. Such a built-in battery pack typically includes at least one unit battery inside and provides the electronic device with a predetermined level of voltage over a reasonable period of time.
Batteries are generally classified as primary or secondary batteries. Primary batteries are commonly known as single-use batteries, and secondary batteries are commonly known as rechargeable batteries. Both primary and secondary batteries may be suitable for use in portable electronic devices. However, the secondary battery is widely adopted because it can be reused and may be, therefore, more economical than single-use batteries. Secondary batteries have been developed using a wide variety of technologies.
Battery technologies currently favored for portable electronic devices include nickel cadmium (Ni—Cd) batteries, nickel metal hydride (Ni—MH) batteries, lithium (Li) and lithium ion (Li-ion) batteries, etc. The lithium batteries have, in particular, been widely employed in the latest generation of electronics devices. A lithium battery may have an operation voltage of 3.6V, which is about three times the operation voltage of the comparable Ni—Cd or Ni—MH batteries. The lithium battery may exhibit a relatively high energy density per unit weight. In a typical lithium battery, a lithium-based oxide may be used as a positive electrode activation material, and a carbon-based material may be used as a negative electrode activation material. Lithium batteries may be classified as liquid electrolyte batteries and polymer electrolyte batteries, depending on the electrolyte used therein. Liquid electrolyte batteries are also known as lithium ion batteries and polymer electrolyte batteries are also known as lithium polymer batteries. The lithium battery may be manufactured in various shapes, e.g., cylindrical, rectangular or prismatic, pouch, etc.
A typical battery may have an electrode assembly, a battery case for housing the electrode assembly and electrolyte injected inside the battery case to give mobility to charge-carrying ions. The electrode assembly may include a positive electrode plate on which a positive activation material is coated, a negative electrode plate on which a negative activation material is coated and a separator interposed between the positive and negative electrode plates. The separator may serve to prevent short circuits between the positive and negative electrode plates and to allow only ions to pass through. The width of the separator of the electrode assembly may be larger width than the widths of the electrode plates, in order to prevent the electrode plates from making contact with each other.
If such a battery suffers an external impact, e.g., by being dropped or hit, it may develop a short circuit. In particular, when the battery suffers an external impact, the separator and the electrode plates may be folded or deformed. This may result in a load being concentrated on corners of a rectangular separator, severely damaging it. As a result of the damage to the separator, the case may make contact with an electrode plate having opposite polarity or the positive and negative electrode plates may make contact with each other, resulting in a short circuit.